Voice operated switching



Jan. 30, 1934. K SANDEMAN AL 1,945,082

VOICE OPERATED SWITCHING Filed Jan. 23, 1931 5 Sheets-Sheet 1 INVENTORS EDWARD K. SANDEMAN FREDERICK G. FILBY 7 ATTORN EY Jan. 30, 1934.

E. K. SANDEMAN ET AL 1,945,082

VOICE OPERATED SWITCHING Filed Jan. 23, 1931 5 Sheets-Sheet 2 FIG. I B

INVENTORS EDWARD K. SANDEMAN FREDERICK G FILBY ATTORNEY Jan. 30, 1934. E. K. SANDEMAN ET AL 1,945,082

VOICE OPERATED SWITCHING Filed Jan. 23, 1931 5 Sheets-Sheet 3 F IG. 2-A

INVENTORS EDWARD K. SANDEMAN FREDERICK G.F|LBY BYJWM ATTORNEY Jan. 30, 1934. I E. K. ESANDEMAN ET AL 1,945,082

VOICE OPERATED SWITCHING Filed Jan. 25, 1931 5 Sheets-Sheet 4 i4 iji 'INVENTORS EDWARD K. SANDEMAN FREDERICK e. FILBY BY?W4%1 ATTORNEY Patented Jan. 35), 1934 Nit) TENT

1,945,082 VOZlCE ()PERATED SWITCHING Edward assignors to Inter- Corporation, New

York, N. 1., a corporation of Delaware Application and in 6 Claims.

This invention relates to switching arrangements for use in electric signalling systems.

It is known that in certain types of signalling systems it is often required to perform switching operations either before or after the signals are transmitted. For instance in a telephone system it is necessary to actuate a number of switching devices so that a suitable circuit is provided for transmitting a given signal to the desired station. Sometimes it is also required to select a given path amongst a plurality of paths leading from the transmitting station to the receiving station.

The switching operations above mentioned may be performed either manually as in manual systems (telephone systems, telegraph systems etc.) or by the intermediary of auxiliary signals sent by mechanically actuated apparatus such as for instance the dial impulses or switchhook impulses used in automatic telephone systems.

It will be clear that the systems referred to necessitate mechanical actuating to perform the required switching operations.

An object of the present invention is to provide an improved arrangement in a signalling system wherein a number of operations such as switching operations may be e iciently performed entirely under the control of the main signals.

According to one feature of the invention means are provided for sending an auxiliary signal or pulse entirely under control of the main signal at the cessation of transmission of the main signal. This auxiliary signal or pulse is adapted to change or allow to he changed the direction in which the system is conditioned for transmission.

According to another feature of the invention means are provided for sending a preliminary pulse or signal for conditioning for reception the apparatus of the station to which the transmitted signal is intended to be sent and a following pulse or signal for restoring to normal the apparatus of said station, said auxiliary pulses or signals being sent entirely under the control of the main signals.

According to another feature of the invention the preliminary and/or following pulse as above may be in the form of a code.

Other features of the invention will be apparent from the following description with reference to the accompanying drawings of which:

Figs. 1A and 1B show terminal equipment for use in connection with a radio link in which the radio transmitter and radio receiver are indicated by RT and RR respectively.

Figs. 2A and 2B are schematics of the circuits January 23, 1931, Serial No. 510,617, Great Britain February 12, 1930 for use at intermediate stations of a submarine cable or other two wire circuit.

Fig. 3 shows the form of the impulses used to actuate certain relays.

Fig. 4 shows a modification of the circuit when used at submarine cable terminations.

Referring to Fig. 1A of the drawings, assume that speech arrives over the line at WE. The speech actua'tes the detector amplifier R1, the output of which is connected through the quick operatequick rel ase relay E and the slow operate-slow release relay F. The operation of the relay E causes contact E3 which is normally broken, to close. This puts earth on relay G through contact Ea of relay F which is normally closed. The operation of relay G causes contact G9 to close, connecting the oscillator 01 to the line. Thus the coded signal is sent into the radio'transmitter and this continues until the, operation of relay F causes the contact F8 to break. The

reaking of this contact allows relay G to release and the pulse to cease. The generation of the following pulse is caused when the output from; R1 ceases. This releases relays E and F causing contact E2 to make, which puts earth through contact F5 of relay F, to relay H. The operation of relay H closes the contact 1-11 and the oscillator 2 is put on to the line through a delay network D2. The pulse continues until slow release relay F allows contact F5 to break. The amplifier A prevents the following pulse from acting back through the delay network D1 and operating the detector amplifier R1. The purpose of the delay network D1 is to hold up the speech whilst the preliminary pulse is sent out, and its delay must be equal to the time of operation of relay 1*. The network D2 delays the following pulse until the last of the speech has passed through Di into the transmitter, and its delay should be equal to delay D1 minus (the time of release of plus the time of operation of E). Di and D2 have been shown in the diagram as two separate networks, but it is possible to dispense with D2 and bridge the oscillator 02 across two points in D1 in such a way that the above condition is-fulfilled. O1 and 02, have in the above, been referred to as oscillators but it should be under stood that in general, these represent any method of generation of the desired form of coded signals.

The arrangements at the receiving end (E-W in Fig. 133) are as follows:-The detector amplifier R2 is tuned to the oscillator 01, and its output causes relays J and K to operate. The operation of relay J breaks contact J1 and, therefore, the output circuit of the detector amplifier R3, which is tuned to receive the following pulse. The relay K in conjunction with relays L, M and N form a selective relay arrangement 1 by means of which the particular code which is being used is picked out. The operation of this chain of relays will be described later. When the pulse causes this relay arrangement to operate, relay N causes contacts N6 and N8 to break, thus removing earth from the two slow release relays S and P. Unless the pulse is of a sufiicient predetermined length the. relays P and S will not release. If, however, P releases, earth is connected to relay K through contact P1 causing X to operate. This switches the line into the receive position. X also closes contact X1, putting earth through contacts T1 and S1 on to itself, thus locking the circuit. If the pulse is of greater length than the predetermined value, the relay S will also release, thus breaking contact S1 and preventing the circuit from locking. When speech has ceased and the following pulse arrives, the output from Rs operates relay Q through contact J1 and by an arrangement of relays U, W and Y, similar to L, M and N, but arranged to receive the code of the following pulse, causes contacts Y1 and Y2 to break. If the pulse is again of sufiicient length this allows slow release relay T to release, thus breaking contact T1 and taking earth oii relay X allowing the contacts to fall back into the transmitting position. If however, the pulse is too long, relay V will also release and contact V1 will make. This shorts contact T1 of relay T and prevents relay X from releasing. It should be noted that the difference the release times of T and V should be less than the release time of X.

In general, the two pulses will be both diiferent in code and in length. For example, in a particular case the preliminary pulse might be 2,000 c. p. s. interrupted 25 c. p. s. lasting for 120 milliseconds whilst the following pulse is 500 c. p. s. interrupted 15 c. p. s. for 200 milliseconds. In this case, the form of the rectified impulses acting on relays K and Q is as shown in Fig. 3 of the draw ings In the first case AB=BC=CD=DE=EF=20 milliseconds,

whereas in the second case AB=BC=CD=DE=EF=33 milliseconds,

. The way in which the selectively relay arrangements operates is as follows:-

Taking the example of a preliminary pulse given above it is necessary that this pulse shall operate the train of relays K, L, M, and N.

Suppose the operate and release times of these relays are K, operate time 2 millisecond, release time 3 milliseconds L, operate time 2 millisecond, release time 19 milliseconds M, operate time 2 millisecond, release time 17 milliseconds N, operate time 2 millisecond, release time 4 milliseconds Now when impulses as described above energize K, it will be alternately operated and released for periods of 21 and 19 milliseconds respectively. The operation of K removes earth from relay L and also operates relay N. After 19 milliseconds L will release taking earth ofi N and energizing relay M. Two milliseconds later M operates and K releases, thus taking earth off M and again en ergizing N. After 17 milliseconds M releases taking earth off N and energizing L and after a further two milliseconds L and K again operate once more energizing N. These operations are then reeated as long as the pulse continues.

During the above process relay N remains continuously operated, for at no time is the current cut off for a period as great as its release time and hence if the length of the pulse is greater than the release time of relay P but less than that of S, then the switching will be accomplished.

Obviously the arrangement may be used for other codes if relays of appropriate operate and release times are employed.

In the case of an intermediate station the arrangements are very similar to the above except that the receiving arrangement, as well as switching the circuit by means of relay X, generates a fresh pulse which proceeds to the distant end of the circuit. This is done by placing the we relays E and F in circuit with the relay X as shown in Fig. 2A and Fig. 2B. These figures show an arrangement for use at an intermediate station, the reference characters being the same as in Fig. 1A and Fig. 1B. A1, A2, A3, A4, A5 and A6 represent the necessary amplifiers, and D is a delay network which holds up the speech while the switching is performed. The generation of the pulse is exactly similar to the previous case. In this case the relay X should be a quick operateslow release relay to allow the following pulse to pass the switch before the line returns to the transmitting position:

In the case-0f the terminal equipments for a submarine cable or other two wire circuit which is terminated in a four-wire line a further modification is necessary to remove any possibility of a lock-up if pulses are sent from the two ends simultaneously or within a period equal to the transmission time of the circuit. This modification consists in placing a quick-operate relay in the output circuit of the amplifier detector in the pulse generating arrangement at one end. The operation of this relay breaks the input circuit of the pulse receiving apparatus at that end. Fig. 4 illustrates this case and the reference characters are as in Figs. 1A, 113, 2A and 2B. Thus, in the figure, for example, if signals are originated simultaneously at the two ends of the circuit switching will only be effected. at the E-W end, the W end pulse receiving apparatus being disabled by the relay Z. For simplicity only one set of pulse generating apparatus has been shown in detail in Fig. 4, the complementary generating and receiving apparatus being shown as blocks and designated PRA and PGA. S. C. represents a submarine cable.

In order to prevent false operation of the system due to momentary cessation or reduction in strength of the signal it may be necessary to introduce a delay in the disabling or changing of the transmitting direction of the system. This can be done conveniently by making the relays K and S operating from detector-amplifier R2 and relay Q operating from detector-amplifier Rs sluggish in operation. Alternatively, of course, any suitable form of relay train may be added in place of these relays.

What is claimed is: I

1. In an electric communication system comprising a plurality of stations, means at one of said stations for sending an auxiliary preliminary signal for conditioning for reception the apparatus at another station to which the transmitted main signals are intended to be sent and an auxiliary following signal for restoring to normal the apparatus of said station, and means entirely under the control of the main signals for controlling said means.

2. A communication system according to claim 1 wherein the auxiliary signals are in the form of code signals and switching means are provided which are responsive only to said code signals for conditioning said apparatus.

3. In an electric communication system comprising a plurality of stations, means at one of said stations for sending an auxiliary preliminary signal in the form of coded impulses, means at another station for responding to said coded impulses, means controlled by said last mentioned means for conditioning the apparatus at said other station for reception of the main signals, and means entirely under the control of the main signals for controlling said first mentioned sending means.

4. A system according to claim 3, wherein the means for responding to coded impulses comprises a chain of relays so constructed and. adjusted that the complete chain is operated only on receipt of a predetermined coded signal.

5. In a system as claimed in claim 3, the combination of a second means at said station for sending an auxiliary following signal in the form of coded impulses, means at said other station for responding to said coded impulses, means controlled by said last mentioned means for conditioning the apparatus at said other station for transmission of main signals therefrom, and means controlled by the cessation of main signals from said first mentioned station for controlling said sending means.

6. In a telephone transmission system, means under control of the voice currents for transmitting an auxiliary preliminary signal automatically with the commencement of talking and means for transmitting an auxiliary following signal automatically with the cessation of talkmg.

EDWARD K. SANDEMAN. FREDERICK G. FILBY. 

